I’m not familiar with the controller settings required for regen, but it may be that with the motor in forward and with “miniscule throttle” and a following wind, the controller could have been charging the batteries up for some time until you switched it to neutral. Assuming flooded cells, at 54.89v, that’s 2.29v/cell, or 6.86v/battery. Fully charged batteries will typically be 2.14v/cell or 6.42v/battery or 51.36v. In your case, you saw 51.7v when in Neutral, which is about right for a fully charged pack. According to charging curves, even a C/40 charge rate (or less) could cause 2.29v/cell, hence for T105 batteries, even less than 5-amp charging rate can cause such voltage rises. I have some 15v/6a charging ‘bricks’ (laptop power supplies) that I’ve used to occasionally equalize series pairs of T105’s on my electric car. I attached this setup after the normal series charger completes its charge. And at 6amps, the batteries will reach 2.5v/cell.
In your case, you may have had well under 5amps of regen charge current, then when you switched to Neutral, no more regen was taking place and the battery voltage relaxed to 2.15v/cell or so.
In case this helps-
-Myles Twete, Portland, Or.
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of acsarfkram
Sent: Sunday, April 24, 2011 6:47 PM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] regen
I had something interesting happen today. I was trying to get some numbers on regeneration with the Watt Meter that I mounted at the helm. I was not able to see any amps recorded. I'm thinking the Turnigy Watt Meter might not be sensitive enough to detect low amps. But with the motor in forward and a miniscule amount of throttle I noticed that the volts were reading 54.89. That seemed odd so I shifted into neutral and after a a few minutes the battery voltage was 51.7. Something is going on. The bank was used for only 2 minutes at the start of the day - there was a nice 12 knot wind over the starboard stern on the way out of the Harbor. Great day, at one point surfing down a wave I saw 9.1 knots on the GPS!
Mark
Santa Cruz
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